In order to investigate soil-gas 222Rn concentraions, Kwanak Campus(Seoul National university), Boeun (Choong-buk) and Gapyung (Kyonggi) areas were selected and classified depending on their base rock types. Radon risk indices of these study areas decrease in the order of Gapyung>Kwanak Campus>Boeun areas, and in the order of rock types as banded gneiss>granite gneiss>garnite>black slate-shale>mica schist>shale-limestone>phyllite-schist. Radon emanating trends with water content and grain size of soils were assessed by modified Morse 3 min method. Radon emanation increases with the increase of water content in soils which is lower than 6∼16 wt.%, and decrease in the range of higher than 6∼16 wt.%. It shows that Rn emanation increases with the decrease of soil grain size. Radioactivity analysis of radionuclides of 238U series in some soil samples shows that radioactive disequilibrium state between 226Ra and 238U exists owinf to different geochemical behavior of each radiomuclide, and, it is necessary to carry out radioactive isotope geochemical approach for soil-gas 222Rn study.
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